Centrifugal Impeller and Centrifugal Blower

ABSTRACT

A centrifugal blower includes an electric motor, a centrifugal impeller driven by the motor, a diffuser mounted to the motor and disposed between the motor and the centrifugal impeller, and a casing mounted to the diffuser. The centrifugal impeller is received in a chamber defined by the diffuser and the casing. the casing defines an opening facing the inlet of the centrifugal impeller. The diffuser has a plurality of passage walls, and a plurality of diffusing passages, each bounded by neighboring passage walls. The diffuser further has at least one mounting portion connected to one of the passage walls. A cross section of each of the diffusing passages is increased form an outer end to an inner end thereof and no throat is formed in each of the diffusing passages.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application is a continuation-in-part ofU.S. patent application Ser. No. 14/500,666, which claims priority toPatent Application No. 201310452740.4 filed in The People's Republic ofChina on Sep. 29, 2013.

FIELD OF THE INVENTION

This invention relates to a blower and in particular, to a centrifugalblower and a centrifugal impeller especially suitable for thecentrifugal blower.

BACKGROUND OF THE INVENTION

A centrifugal blower includes a motor and a centrifugal impeller. Thecentrifugal impeller includes a cover, a base and a plurality of bladeswhich are arranged between the cover and the base and connect the coverand the base. The cover has an inlet for entrance of air flow. Ends ofthe blades adjacent the center of the impeller define a cavity facingthe inlet of the cover.

The centrifugal impeller is driven by the motor. A low pressure zone isformed at the center of the impeller. Air outside the blower enters intothe cavity via the inlet of the impeller, then flows into the flowpassages formed by the blades and is eventually discharged from theimpeller.

One of the disadvantages of the current design is that the efficiency ofthe blower is low.

SUMMARY OF THE INVENTION

Accordingly, in one aspect thereof, the present invention provides acentrifugal blower including an electric motor, a centrifugal impellerdriven by the motor, a diffuser mounted to the motor and disposedbetween the motor and the centrifugal impeller, and a casing mounted tothe diffuser. The centrifugal impeller is received in a chamber definedby the diffuser and the casing. the casing defines an opening facing theinlet of the centrifugal impeller. The diffuser has a plurality ofpassage walls, and a plurality of diffusing passages, each bounded byneighboring passage walls. The diffuser further has at least onemounting portion connected to one of the passage walls. A cross sectionof each of the diffusing passages is increased form an outer end to aninner end thereof and no throat is formed in each of the diffusingpassages.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to figures of the accompanying drawings. Inthe figures, identical structures, elements or parts that appear in morethan one figure are generally labeled with a same reference numeral inall the figures in which they appear. Dimensions of components andfeatures shown in the figures are generally chosen for convenience andclarity of presentation and are not necessarily shown to scale. Thefigures are listed below.

FIG. 1 illustrates a blower in accordance with a preferred embodiment ofthe present invention;

FIG. 2 shows the blower of FIG. 1, with a casing removed;

FIG. 3 shows a centrifugal impeller being a part of the blower of FIG.1;

FIG. 4 is a partial view of a part of the impeller of FIG. 3;

FIG. 5 is a view of the impeller of FIG. 3, with a cover removed;

FIG. 6 is a plan view of the impeller of FIG. 3, with the cover removed;

FIG. 7 is a view of an impeller side of a diffuser, being a part of theblower of FIG. 1;

FIG. 8 is a view of a motor side of the diffuser of FIG. 7;

FIG. 9 is a plan view of the motor side of the diffuser of FIG. 7;

FIG. 10 is a plan view of the diffuser and motor parts superimposed; and

FIG. 11 shows the blower of FIG. 1 viewed from another angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a centrifugal blower 20 in accordance with apreferred embodiment of the present invention comprises an electricmotor, a centrifugal impeller 23 mounted to a shaft of a rotor of themotor, a diffuser 31 mounted to the motor and arranged between the motorand the impeller 23, and a casing 21 mounted to the diffuser 31. Theimpeller 23 is received in a chamber 22 defined by the diffuser 31 andthe casing 21. The casing 21 has an opening 19 facing an inlet of theimpeller 23.

In the embodiment, the motor is a universal motor. A stator of the motorcomprises a stator core 41, stator windings 44 wound about teeth of thestator core 41, an end cap 43 mounted to the stator core 41, and a brushassembly 45 mounted to the end cap 43. In this embodiment, the diffuser31 functions as another end cap of the motor. The diffuser 31 and endcap 43 are mounted to the axial ends of the stator core 41. The diffuser31 has two projected mounting portions 38 for mounting diffuser 31 tothe stator core 41. The rotor of the motor comprises a shaft, acommutator 51 fixed to the shaft, a rotor core and rotor windings (notshown in the figures). The shaft is mounted to the end cap 43 and thediffuser 31 via bearings such that the rotor may rotate relative to thestator.

The diameter of the diffuser 31 is slightly greater than that of theimpeller 23. A plurality of guide holes 34 a adjacent outlets of theimpeller 23 are formed at the outer periphery of the diffuser 31. Airflowing out from the outlets of the impeller 23 flows from the impellerside of the diffuser 31 to the motor side of the diffuser 31 the guideholes 34 a.

Referring to FIGS. 3 and 4, the impeller 23 comprises a cover 25, a base24 opposite the cover 25, and a plurality of blades 26. The cover 25 hasan inlet 27 formed at a center thereof and facing the opening 19 of thecasing 21. The plurality of blades 26 surrounding the inlet are disposedbetween and connect the cover 25 and the base 24. Ends of the blades 26adjacent the center of the impeller 23 form a cavity 28 in communicationwith the inlet of the impeller 23. An inlet edge 26 e of the inner endof each blade 26 adjacent the center of the impeller is inclinedrelative to the base 24 of the impeller 23. Therefore, the dimension ofthe cavity gradually decreases along the direction from the cover 25 tothe base 24. By this configuration, when the impeller 23 rotates, theair flows into the cavity and then into the flow passages formed by theblades 26. The amount of air in the cavity gradually decreases along thedirection towards the base 24. As the change of the amount of air in thecavity matches the change of the dimension of the cavity, the air flowis more stable and uniform.

The inlet edge 26 e of each blade 26 forms an angle θ with the normalline L1 of the base 24 and forms an angle γ with the end surface of thebase 24. The line L2 in the figure represents the imaging direction ofthe inlet edge 26 e on the base 24. As the normal line L1 of the base isperpendicular to the line L2, the sum of the angle θ and the angle γequals 90°. Experiments show that the impeller 23 has good performanceand high efficiency when the angle γ is in the range of 55° to 75° andthe angle θ is accordingly in the range of 35° to 15°.

Preferably, the angle γ is in the range of 62° to 70° and the angle θ isaccordingly in the range of 28° to 20°.

More preferably, the angle γ is in the range of 65° to 68° and the angleθ is accordingly in the range of 25° to 22°.

Referring to FIGS. 5 and 6, each blade 26 includes a first arc segment26 a and a second arc segment 26 b which have different radii. The firstarc segment 26 a is located at the radially inner end of the blade 26adjacent the center of the impeller 23 and the second arc segment 26 bis located at the radially outer end of the blade 26 away from thecenter of the impeller 23. Compared with the traditional blade with asingle arc segment, the blades 26 in the present invention have betterperformance and higher efficiency.

In the embodiment, the radius R2 of the second arc segment 26 b isgreater than the radius R1 of the first arc segment 26 a.

Referring to FIGS. 7 and 8, the diffuser 16 has an end wall 32 and anannular side wall 29 extending from the end wall 32 towards the motor.The end wall 32 and the side wall 29 form a hollow space 30 facing themotor. A bearing for supporting the shaft of the rotor of the motor ismounted in a recess at the center of the end wall 32. The side wall 29has crimping recesses 35 facing the motor. During the assembly, portionsof the casing 21 is crimped into the recesses 35 (see FIG. 1). The sidewall further has a plurality of guide slopes 33 inclined from the endsurface of the end wall 32 towards the motor and a plurality of guideholes 34 at the end of the guide slopes 33. Referring back to FIGS. 1and 2, the end wall 32 of the diffuser 31 is adjacent to the base 24 ofthe impeller 23. The guide slopes 33 and the guide holes 34 a areadjacent to the outlets of the impeller 23. Air flowing out from theoutlets of the impeller 23 flows into the guide holes 34 a under theguidance of the guide slopes 33.

Referring to FIGS. 8 and 9, a plurality of smoothly curved diffusingpassages 34 having outer ends and inner ends are formed in the hollowspace of the diffuser 31. The outer ends of the diffusing passages 34are in communication with corresponding guide holes 34 a and the innerends of the diffusing passages 34 are in communication with one another.Therefore, air flow from the impeller 23 is able to flow from theimpeller side of the diffuser 31 to the motor side of the diffuser 31via the guide holes 34 a, then flows into the center of the diffuser 31via the diffusing passages 34, and passes through the motor in the axialdirection to cool the motor. To reduce the noise caused by theresistance of the air flow and improve the air diffusion efficiency, thecross section of each of the diffusing passages 34 is graduallyincreased form the outer end to the inner end thereof. No throat isformed in each of the diffusing passages 34.

The diffuser 31 includes plurality of passage walls 36 at the sidefacing the motor to bound the diffusing passages 34. Inner ends of thepassage walls 36 are spaced from one another and define a space at thecenter of the diffuser 31. The two mounting portions 38 are respectivelyconnected to the inner ends of two of passage walls 36 and diametricallyopposite to each other. Each of the mounting portions 38 has acylindrical surface 38 a protrudes towards the center of the diffuser31. The cylindrical surface 38 a of each mounting portion 38 isconnected to the corresponding one of the passage walls 36 with a smoothtransition to avoid a throat occurring at the corresponding one of thediffusing passages 34 bounded by said one of the passage walls 36. Eachof the corresponding passage walls 36 connected to the mounting portion38 has a variable thickness, which gradually increases from the outerend to the inner end thereof. Therefore, each corresponding passage wall36 together with the mounting portion 38 connect thereto has araindrop-shaped contour, which helps to reduce the resistance of the airflow.

Referring to FIGS. 8 to 11, Each of the mounting portions 38 defines amounting recess 39 for positioning the stator core 41 of the motor. Thestator of the motor includes a stator core 41 and two stator windings 44wound about teeth of the stator core 41. Axial ends of the two statorwindings 44 extend into the space defined by the inner ends of thepassage walls 36 of the diffuser 31 and are located at two sides of themounting portions 38 in the circumferential direction. The two mountingportions 38 are circumferentially arranged between the two statorwindings 44 for guiding the air flow in the diffusing passages 34 to thestator windings 44. The air flow is thus concentrated on two sides of avirtual line connecting the two mounting portions 38 so as to bettercool the stator windings 44.

Further, each of the mounting portions 38 defines a mounting hole 37,which enable each of the mounting portions 38 to mate with a fastener tofixed the diffuser to the motor. In the embodiment, the mounting holes37 are located in the mounting recesses 39. During assembly, thefasteners 60, such as bolts or screws, pass through the mounting holes37 of the mounting portions 38 and the stator core 41 to be fastened tothe end cap 43 so as to fix the diffuser 31, the stator core 41 and theend cap 43 together.

In the description and claims of the present application, each of theverbs “comprise”, “include”, “contain” and “have”, and variationsthereof, are used in an inclusive sense, to specify the presence of thestated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or morepreferred embodiments, it should be appreciated by those skilled in theart that various modifications are possible. Therefore, the scope of theinvention is to be determined by reference to the claims that follow.

1. A centrifugal blower comprising: an electric motor; a centrifugalimpeller driven by the motor; a diffuser mounted to the motor anddisposed between the motor and the centrifugal impeller; and a casingmounted to the diffuser, the centrifugal impeller being received in achamber defined by the diffuser and the casing, the casing having anopening facing the inlet of the centrifugal impeller; wherein thediffuser has a plurality of passage walls, and a plurality of diffusingpassages, each bounded by neighboring passage walls, the diffuserfurther has at least one mounting portion connected to one of thepassage walls, a cross section of each of the diffusing passages isincreased form an outer end to an inner end thereof and no throat isformed in each of the diffusing passages.
 2. The centrifugal blower ofclaim 1, wherein said at least one mounting portion is connected to aninner ends of the corresponding one of the passage walls, each of saidat least one mounting portion comprises a cylindrical surface protrudestowards the center of the diffuser.
 3. The centrifugal blower of claim2, wherein the cylindrical surface is connected to the corresponding oneof the passage walls with a smooth transition; the passage wallconnected to said at least one mounting portion has a variablethickness, which gradually increases from the outer end to the inner endthereof; said at least one mounting portion together with thecorresponding passage wall connected thereto has a raindrop-shapedcontour.
 4. The centrifugal blower of claim 1, wherein said at least onemounting portion comprises two mounting portions respectively connectedto the inner ends of two of passage walls and diametrically opposite toeach other.
 5. The centrifugal blower of claim 1, wherein thecentrifugal impeller comprises a cover defining an inlet; a baseopposite the cover; and a plurality of blades sandwiching between thecover and the base, the plurality of blades surrounding the inlet, inletedges of ends of the blades adjacent the center of the centrifugalimpeller defining a cavity in communication with the inlet, thedimension of the cavity gradually decreasing in the direction from thecover towards the base.
 6. The centrifugal blower of claim 5, whereineach inlet edge forms an angle γ with the base in the range of 55° to75°.
 7. The centrifugal blower of claim 6, wherein each inlet edge formsan angle γ with the base in the range of 62° to 70°.
 8. The centrifugalblower of claim 7, wherein each inlet edge forms an angle γ with thebase in the range of 65° to 68°.
 9. The centrifugal blower of claim 5,wherein each blade has a thickness, which is invariable alonglongitudinal direction thereof, and comprises first and second arcsegments which have different radii, the first arc segment being locatedat a radially inner portion of the blade, and the second arc segmentbeing located at a radially outer portion of the blade.
 10. Thecentrifugal blower of claim 9, wherein the radius of the second arcsegment is greater than the radius of the first arc segment.
 11. Thecentrifugal blower of claim 1, wherein the diffuser defines a pluralityof guide holes, the air flow generated by the centrifugal impellerflowing from one side of the diffuser adjacent the centrifugal impellerto the side of the diffuser adjacent the motor via the guide holes,outer ends of the diffusing passages being in communication withcorresponding guide holes and inner ends of the diffusing passages beingin communication with one another.
 12. The centrifugal blower of claim4, wherein the motor comprises a stator comprising a stator core andstator windings wound about teeth of the stator core, and the twomounting portions are respectively located at gaps between the statorwindings so as to guide the air flow in the diffusing passages to thestator windings.
 13. The centrifugal blower of claim 12, wherein thediffuser has an end wall and a side wall extending from the end walltowards the motor, the passage walls and the diffusing passages beingformed inside a space defined by the end wall and the side wall, axialends of the stator windings extending into a space defined by the innerends of the passage walls and located at two sides of the mountingportions.
 14. The centrifugal blower of claim 13, wherein the side wallhas a plurality of guide slopes which extends from the end wall towardsthe motor in a direction inclined as regard to an axial direction of thediffuser, the guide holes being located at the ends of the guide slopesaway from the end wall.
 15. The centrifugal blower of claim 1, whereineach of said at least one mounting portion defines a mounting hole forreceiving a fastener for fixing the diffuser to the motor.